Controlled temperature fluid flow directing member



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CONTROLLED TEMPERATURE FLUID FLOW DIRECTING MEMBER Filed Dec. 6, 1949TEMPERATURE 'r B5 -%%4. LL

United States Patent CONTROLLED TEMPERATURE FLUID FLOW DIRECTING NIEMBERMilton S. Roush, Painesville, Ohio, assignor to Thompson Products, Inc.,Cleveland, Ohio, a corporation of Ohio Application December 6, 1949,Serial No. 131,309

2 Claims. (Cl. 253-3915) The present invention relates to a controlledtemperature fluid flow directing member and more particularly to a fluidflow directing member provided with means for controlling thetemperature of the member when it is employed in a heated working fluid.

As is well known, the fluid flow directing members of a gas turbine, ajet turbine, a supercharger,.or the like, are subjected to a heatedworking fluid, usually a burning gas, acting thereagainst. Since theefliciency of the turbine or supercharger increases with the heatcontent of the working fluid, it is desirable that the fluid contact theflow directing member at the maximum temperature at which the member iscapable of functioning without excessive distortion and/or stressfailure. Heretofore, the heat resistance properties of such members havelimited the maximum temperature of the working fluid actingthereagainst, and even at such temperatures the occurrence of local hotspots has been a frequent reason for failure of the flow directingmembers.

The present invention now provides means whereby a fluid flow directingmember, such as a turbine bucket or vane, is maintained at a uniformtemperature throughout to prevent or immediately correct the occurrenceof local hot spots. In general, the bucket or vane of the presentinvention includes a root portion for securing the bucket to itsrotatable supporting means and a blade portion projecting beyond theroot to direct the working fluid through the apparatus in which thebucket is employed. The bucket is provided with an interior cavity whichmay include a reservoir formed in the root and a branching passageformed in the blade, the reservoir and passage being adapted to receivea body of a suitable coolant, such as sodium, which is fluid at thetemperatures developed on the blade during operation. In some instancesthe root reservoir can be omitted as, for example, where heat is not tobe dissipated out of the root.

Upon the development of a local hot spot on the blade, that portion ofthe coolant contacting the hot spot is vaporized and passes to a coolerportion of the bucket for condensation, while relatively cool coolantunder the tremendous centrifugal force created in the rapidly rotatingturbine wheel fills the space vacated by the vaporized coolant. Thevaporization of the coolant, due to its high latent heat ofvaporization, creates a cooling effect, and the incoming coolant removesmore heat by conduction and convection to reduce the temperature ofsurrounding portions of the blade. The maximum temperature which may bedeveloped in the blade is predetermined by evacuation of the reservoirand the branched passage connected thereto, since for any given coolantthe vaporizing or boiling temperature is directly proportional to thepressure to which it is subjected.

It is, therefore, an important object of the present invention toprovide an improved controlled temperature fluid flow directing member.

Another important object of the present invention is to provide animproved controlled temperature fluid flow 2,744,723 Patented May 8,1956 directing member for disposition in a heated working fluid, themember including a coolant in eflicient heat transfer relation to theportions thereof which are exposed to the working fluid to prevent theoccurrence of local hot spots during operation.

It is a further important object of the'present invention to provide acontrolled temperature fluid flow directing member including a bladeportion exposed to a heated Working fluid and a root portion secured torotatable means maintaining the blade in the working fluid; the rootportion may have an interior coolant reservoir therein and the bladeportion has a branched passageway which may communicate with thereservoir for conducting coolant from the reservoir into eflicient heattransfer relation with substantially all of the exposedportions of saidblade. The branched passageway above may be used as a heat transferringmedia.

Still another important object of the present invention is to provide amethod for the cooling of a fluid flow directing member having portionsexposed to a heated working fluid, including the steps of disposing abody of coolant in efficient heat transfer relation to heated portionsof said member and determining the maximum tem peratures to be developedin said member by controlling the pressure upon said coolant.

Other and further important objects of this invention will be apparentfrom the disclosures in the specification and the accompanying drawings.

On the drawings:

Figure l'is a side elevational view, with parts broken away, of a fluidflow directing member of the present invention;

Figure 2 is an elevational view similar to Figure 1 illustrating amodified form of a fluid flow directing member of the present invention;

Figure 3 is a sectional view taken along the plane lIl-III of Figure 2;

Figure 4 is a sectional view taken along the plane IVIV of Figure 2;

Figure 5 is a sectional view of an apparatus for filling a flowdirecting member of Figures 14 with coolant; and

Figure 6 is a graphical representation-of the boiling point curve of acoolant suitable for use in a fluid flow directing member of the presentinvention.

As shown on the drawings:

In Figure 1, reference numeral 10 refers generally to a fluid flowdirecting member, specifically a turbine blade or bucket, of the presentinvention including a root portion 11 and an air foil section or bladeportion 12.

The root end portion 11 of the bucket 10 is massive and is provided withsuperimposed stepped notches 13 in the lateral faces thereof formounting the bucket 10 in a conventional manner, as on a turbine wheel,a nozzle diaphragm, or the like. The blade or air foil portion 12 isappropriately shaped to efliciently direct the working fluid through theapparatus with which the bucket 10 is employed, as through a turbinewheel. The blade portion 12 has a concave face 14 and a convex face 15designed and contoured to provide the desired aerodynamiccharacteristics of the blade, the blade being of relatively thincross-sectional thickness. The bucket or vane 1% may be made of asuitable heat resistant alloy, such as Vitallium (30% Cr, 6% Mo, balanceCo) or similar alloys in which a portion of the cobalt is replaced withnickel and/ or in which the molybdenum is replaced with tungsten.

The root portion 11 is provided with an interior coolant reservoir 16directly underlying the blade 12 for containing a body of a coolant C,and the blade portion 12 is provided with an interior cavity defined bya plurality of interconnected, branched channels arranged in a.generally rectangular pattern. More particularly, the cavity is definedby a main vertical channel 17 communieating with the reservoir 15 andextending along the length of the blade 12 and auxiliary channels 13extending parallel to the main channel 17 and transverse connectingchannels 19 connecting the channels 17 and 18. The interconnectingchannels 17, 18 and 19 thus define a grid network communicating with thereservoir 16 and closely underlying the concave and convex exteriorsurfaces of the blade 12.

A modified form of interior blade cavity is shown in Figures 2 and 3 ofthe drawing in which identical reference numerals refer to identicalportions of the apparatus as hereinbefore described. In this form of thebucket 10, the cavity within the blade 12 takes the form of a mainchannel 20 extending interiorly of the blade 12 along the length thereofand branched auxiliary channels 21 extending from the main channel 20toward the leading and trailing edges of the blade 12.

The grid network of channels 17 and the branched channels 21 terminatein spaced relation from the root portion 11 so as to leave a solid basesection or area on the vane portion 12 adjacent the root portion 11.This solid base section or area is pierced only by a passage joining thechannels with the reservoir chamber in the root portion.

The channels are arranged in the vane portion 12 to be separated bynumerous solid vane areas which rigidity the opposed vane faces againstcollapse.

If desired, the reservoir 16 and the branching passages 1719 and 20-21may be zinc or silver coated to permit wetting of the coating withsodium or a similar coolant, thus enhancing heat transfer.

In Figure of the drawings, an apparatus for filling the reservoir 16 andthe connecting gridwork with a suitable coolant is shown. As shown inFigure 5, communication of the reservoir 16 with the exterior of theblade is provided through a. port 22 which is adapted to be employed infilling the reservoir 1.6 with a suitable coolant, the port 22 beinglater closed by means of a ball shaped plug 23. A filling nipple 24 inthe form of a generally rectangular block, recessed as at 25 to fit overthe end of the root 11 of the blade 10, is provided with side conduits25 and 27 communicating with a central chamber 28 adapted to overlie theport 22 when the block is positioned on the blade. The chamber 28 has abottom opening 29 registering with the port 22 when the block 24 ispositioned on the root 11. A tube 30 extends into the chamber 28 abovethe opening 29 to feed sodium or the like coolant through the openinginto the port 22. The conduit 26 is connected to a suitable source ofvacuum and the conduit 27 is closed and preferably made of glass. Amagnet M is effective to hold the ball plug 23 at the closed end of theconduit until needed whereupon it can then be used to impel the ballinto the port 22. An induction coil C surrounds the blade end to fusethe plug 23 to the port 22. if a nonmagnetic plug is used such as acopper plug a magnetic pusher in the tube 22 can be used to impel theball.

To fill the reservoir 16 and the passage of the blade 12, the reservoirand the connecting passageways are first evacuated by means of theconduit 2'6 to a desired degree of vacuum and molten sodium isintroduced through the conduit 30 under atmospheric pressures or undersuper-atmospheric pressures as desired. When the desired amount ofsodium or of the coolant has been metered through the conduit 30 intothe reservoir 16, the plug 23 is welded to the blade, to close thereservoir 16 and the communicating passageways of the blade 1-2.

The evacuation of the reservoir 16 and the connecting passageways notonly insures the uniform introduction of molten coolant into thereservoir and the reduced connecting passages of the blade 12, but whenregulated it also controls the maximum operating temperature for anyportion of the blade 12. In Figure 6, applicant has illustrated theliquid-vapor phase diagram of sodium, which is employed as the preferredcoolant in the bucket 10 of the present invention. From this diagram, inwhich reference numeral 33 refers to the boiling point curve of sodium,it will be seen that the boiling point of sodium decreases in proportionto a decrease in the pressure to which the sodium is subjected. Theliquid lapor diagrams of other suitable coolants, such assodium-potassium eutectic, Inorganic salts, and the like, show thesimilar decrease in boiling point as a function of decreasing pressure.

The relation of pressure to boiling point of sodium, as illustrated inFigure 6, may also be expressed in tabulated form, as follows:

Table Pressuremm. Hg: Temperature-F. 2 900 The operation of the improvedcontrol temperature fluid flow directing member of the present inventionwill be readily understood from the foregoing description. If thetemperature of the air foil exceeds the boiling temperature of sodium atthe pressure to which the sodium is subjected, the resulting sodiumvapors would immediately pass to a cooler portion of the bucket andcondense and the centrifugal force will cause a flow of relatively coolmolten sodium to the hot spot to reduce the temperature thereof withconvection currents within the molten sodium still further dissipatingthe local heat developed. The very high latent heat of vaporization ofsodium, namely, 1100 calories per gram at 880 C., insures the rapidremoval of heat from the local hot spot and the immediate dissipation ofthis heat.

The reservoir if used serves to cool the entire bucket, inasmuch as itis located in the root out of the path of the heated working fluid andreceives relatively cool fluid thereagainst, such as air from the axialflow compressor of a jet turbine. Cooling of the reservoir may befacilitated by the provision of a plurality of coolant air passages orbores 31 extending longitudinally of the root 11 alongside the reservoir16, as illustrated in Figures 2-4 of the drawing. A further coolingeffect may be obtained by providing an arcuate air scoop 32 extendingacross the leading edge of the root section of the bucket of Figure 2 todirect ambient fluid coolant into the bores 31.

When evacuating the coolant containing passages of the blade 12 and thereservoir 16, it is desirable to provide a small unfilled space A in theblade, and, during rotation of the turbine, centrifugal forces willmaintain coolant in the passages 1719 and 20-21 rather than in the rootreservoir 16, so that eificient cooling of the blade portion 12 of thebucket 10 is insured. Further, in the branched passage design asembodied in Figure 2 of the drawings, centrifugal force tends to aid themovement of coolant fluid outwardly through the auxiliary passages 21since they are inclined outwardly of the blade 12 from the reservoir 16.The unfilled evacuated space A will be substantially filled with coolantvapor when the blade is heated to a temperature greater than the boilingpoint of the coolant at the pressure Within the space A. The unfilledspace A is always desirable as an expansion chamber.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the concepts of the presentinvention.

I claim as my invention:

1. A turbine blade for disposition in the heated working fluid of a gasturbine engine or the like which comprises a vane portion of air foilshape and an integral anchoring root portion at one end of the vaneportion, said vane portion having vane faces exposed during operation tohot working fluid of the gas turbine engine, said root portion beingthicker and more massive than the vane portion and in operation notbeing exposed to the hot working fluid of the gas turbine engine, areservoir chamber in said root portion occupying themajor volume of theroot portion to accommodate a substantial charge of coolant, a pluralityof interconnected small passages in the vane portion separated bynumerous solid vane material areas rigidifying the opposed vane facesagainst collapse by the force of the working fluid, said interconnectedpassages terminating in spaced relation from the root portion to providea solid base section adjacent the root portion, a single passage throughsaid solid base section connecting the interconnected passages with thereservoir chamber, cooling passages in said root portion adjacent theperiphery of the reservoir chamber, a scoop extending across an edge ofthe root portion adapted to direct adjacent ambient fluid into saidcooling passages, a filling passage in the blade extending to theexterior of the blade and communicating with the reservoir chamber forintroducing coolant to said reservoir chamber and said interconnectedpassages, and a closure for said filling passage to seal the coolant inthe blade, whereby said colant will transfer heat from the vane portionexposed to the working fluid to the root portion and said ambient fluiddirected into the cooling passages will dissipate heat from the coolantthereby eliminating local hot spots in the vane portion without reducingthe collapse resistance of the vane portion.

2. A turbine bucket for a gas turbine engine which comprises a vaneportion of air foil section and an integral massive root portion at oneend of the vane portion, said root portion being hollow to provide areservoir chamber occupying substantially the entire volume of the rootportion, said vane portion having a plurality of small interconnectedpassages therein, said passages terminating in spaced relation from theroot portion to provide a solid base portion on the vane, a single smallpassage in said solid base portion connecting the interconnectedpassages with the reservoir chamber, said interconnected passages beingseparated by solid vane sections rigidifying the vane portion againstcollapse, a plurality of cooling passages extending through the rootportion adjacent the periphery of the reservoir chamber therein, saidpassages adapted to receive cooling fluid therethrough for dissipatingheat from the reservoir, a filling passage extending to the exterior ofthe bucket and communicating with the reservoir chamber, and a plugsealing said passage, whereby coolant encased in the reservoir can flowthrough the interconnected passages to dissipate heat from the vane andminimize development of local hot spots in the vane areas.

References Cited in the file of this patent UNITED STATES PATENTS2,407,164 Kimball Sept. 3, 1946 2,407,531 Berimann Sept. 10, 19462,501,038 Fransson Mar. 21, 1950 2,565,594 Constant Aug. 28, 1951FOREIGN PATENTS 544,940 Germany Feb. 26, 1932 594,931 Germany Mar. 23,1934 610,737 Great Britain Oct. 20, 1948

